Solid ink or phase change ink printers conventionally receive marking material in a form known as an ink stick. The ink stick is a solid or semi-solid structure that may have any convenient shape (e.g., a pellet, block, brick, cube, or any other geometric structure) for handling and loading into the printer. During use, ink sticks are inserted through an insertion opening of an ink loader for the printer and pushed or slid along a feed channel by a feed mechanism and/or gravity toward an ink melting assembly in the printer. The ink melting assembly melts the solid ink stick into a liquid that is delivered to a print head for jetting onto a recording medium.
One difficulty faced in solid ink technology is identification and authentication of ink sticks to ensure the correct loading and compatibility of an ink stick with the imaging device in which it is used. For example, unlike powdered or liquid marking materials, the solid form of ink sticks allows the ink sticks to be handled and loaded into a phase change ink printer without the need for a container or cartridge, as is typically required for liquid ink or powdered toner. In addition, the entire ink stick may be melted and consumed, with no need to dispose of, or recycle, any container. Eliminating the need for a container provides many advantages to the use of ink sticks. Containers or cartridges, however, may be provided with electronic tags, barcodes, etc. that may be used to identify and/or authenticate the ink contained therein. Without the use of a container, the mechanisms for authenticating or otherwise identifying the ink stick may be limited.
Provisions have been made to facilitate the authentication and/or identification of ink sticks so that ink sticks are correctly loaded into the intended feed channel and to ensure that the ink sticks are compatible with the printer in which they are used. One provision is generally directed toward excluding wrong colored or incompatible ink sticks from being inserted into the feed channels of the printer. For example, the correct loading of ink sticks has been accomplished by incorporating keying features into the exterior surface of an ink stick. These features are protuberances or indentations that are located in different positions on an ink stick. For example, FIG. 9 shows an embodiment of an ink stick 2 that includes a keying feature 4 that is in the form of a notch that extends along a side surface of the ink stick. Corresponding key elements 6 are positioned on the perimeter of the opening 8 through which the ink stick 2 is inserted. An ink stick that does not have the appropriate key elements in the correct position for the particular insertion opening is excluded from insertion.
While the use of keying features on ink sticks may be effective in ensuring that ink sticks are correctly loaded and compatible with the printer in which they are used, the use of keying features is limited in that the “authentication” of the ink stick cannot be done without access to the printer to see if the keying features on the ink stick match the keying features of the ink loader. In addition, in order to be effective in excluding ink sticks, the key elements are relatively large. Due to the soft, waxy nature of the ink stick body, key features, such as the key feature of FIG. 3, may be casually or easily modified or added to an existing ink stick by milling, cutting, melting and reforming, or otherwise removing material in a shape complementary to keying shapes incorporated into insertion openings. Visual inspections of the ink stick thereafter may be incapable of detecting such a modification.
In addition, world markets have created a situation where ink sticks may be sold under different marketing programs at various price points. Thus, ink sticks having substantially the same configuration may be sold in different markets at different prices. The identification and/or authentication of Ink sticks intended for sale in different markets and/or at different prices has been accomplished by incorporating different keying features into the ink sticks. Selling ink sticks at different prices in different markets, however, offers the undesired opportunity for enterprising entities to purchase ink sticks at a lower price in one market, modifying the ink sticks to include the keying features of ink sticks sold in a different market and/or at a different price point, and reselling the modified ink sticks in the different market at a higher price for monetary gain. Such behavior, described as arbitrage, can cost a company a significant amount of money in lost revenue and profit. Additionally, this can be very harmful and disruptive to legitimate distributors and resellers.